I tend to mentally (or out loud, if I'm not surrounded by people who would try to have me committed) recite "Nam mô A di đà Phật" (as pronounced by the Vietnamese) pretty much any time I'm not actively doing something else with my mind. I'm not familiar with the mantra -- my Vietnamese friends have always called the recitation a mantra so I suppose it is practiced differently by different groups.
My suggestion would be to stick with the one that resonates with you the most, or the one that is practiced by your own local sangha.
In either case, I presume the mantra you typed means "Homage to Amida Buddha" or similar.
Be well, friend.